interesting way of doing fertilizer for a lawn. I think perhaps its a bit to complicated for a home owner to have installed. The cost of this may be a deterrent as well. I can understand using this on golf courses and very LARGE properties as its hard to get good coverage with machines or walk behind methods.
Also the control of chemicals on lawns is a science that is regulated by laws and mixtures of fertilizers and insect control methods must be carefully monitored. Windy days etc can cause these products to blow onto neighboring lawns and could adversely effect them.
Easy is not always better I would think in this case.
as a DIY you can do it. It would require that you make sure you use the correct back flow so that the fertilizer does not back flow into the main line of your water.
Here is a pretty reasonable system set up, there are actually quite a few different brands for this type set up